1. Field of the Invention:
The present invention pertains to conveyor belts, especially those used in refrigeration apparatus, and more particularly in helical conveyor belt apparatus for use in spiral freezers.
2. Description of the Related Art:
Commercial refrigeration apparatus frequently employs conveyor belts to continuously move product through the refrigerated environment, in order to increase freezer throughput. A need has arisen for nonlinear conveyor arrangements which increase the residence time of products in the refrigerated environment. In such conveyor arrangements, the conveyor belt transporting products through the enclosure is made to traverse one or more helical paths, commonly termed "spiral" paths in the industry. So-called spiral freezers employ insulated enclosures which reduce the exterior surface area while increasing the interior volume in which the refrigerated environment is contained.
Conveyor belts in spiral freezers must undergo a change in configuration at the point of transition where a straight line path section entering the refrigerated environment enters the helical path section within the enclosure interior. The change in configuration requires that the conveyor belt undergo a contraction at its radially inner edge and/or an expansion at its outer edge. It is important that such transitions be smooth and do not disturb products carried on the conveyor belt. Frequently, a transition of the type referred to above is accompanied by a relative movement of components internal to the belt conveyor. More specifically, those components forming the upper surface of the conveyor belt, that surface in contact with the products being cooled by the refrigeration apparatus, undergo a relative movement along the length of the conveyor belt, and hence may disturb products borne by the conveyor belt.
There have been continuing efforts to reduce disturbances at the conveyor belt support surface. For example, commonly assigned U.S. Pat. No. 4,878,362 provides a conveyor belt so constructed that upon entering a helical path section from a straight line path section, the conveyor belt undergoes expansion only. The conveyor belt includes a plurality of transverse rods having ends located at lateral edges of the conveyor belt. Bent wire sections are wrapped about adjacent pairs of transverse rods and interconnect the rods to form an open weave support surface at the upper edge of the conveyor belt. The bent wire sections resemble a conical wrapping of wire wound with a relatively loose pitch, flattened at its top portion, to form an upper discontinuous planar support surface. The upper planar surface is the product's support surface and, since the belt undergoes expansion only at the transition point, a minimum disturbance to products on the belt is experienced.
Although the conveyor belt of U.S. Pat. No. 4,878,362 has been met with wide acceptance in the industry, certain improvements have been sought. For example, in the bent wire sections of U.S. Pat. No. 4,878,362, the lower portions of the bent wire sections are bent to form an inverted U-shape, the bight portion of which is aligned generally coplanar with the support surface of the belt overlay. While representing a significant improvement in minimizing the disturbance to certain products carried by the conveyor belt, attention has been focused on further reducing disturbance to delicate products such as meat patties, and to accommodate products of relatively small size.